browse: Add UI components to retrieve vault bundles (WIP)

Integration of new GUI components in order to cook and retrieve
bundles from the SWH vault:

• add buttons to request the cooking of directory/revision bundles in relevant browse views: directory, revision
• use modals to get user confirmation and provide optional email for download ready notification
• add a new tab 'Vault' in the main browse interface to report the status of cooking tasks and offer download links once they are available

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